Patch correcting bootcd setup silent fail while can't format given partition

When bootcd setup found it can't format the given partition it silently goes to last page.

Implemented the dialog that will show now a warning message about failed format operation.

See attached patch for this;
Thanks for applying the patch to the trunk.

One example of where this thing could happen: The case I discovered, is the bootcd running in VM under Windows Vista+, the host windows always lock the partitions so reactos can't do write operation on it ( starting from second sector, in fact). Now at least we could have a warning dialog.